Method for making thin wall flexible bearing liners



June 23, 1970 N FISHER ET AL 3,516,137

METHOD FOR MAKING THIN WALL FLEXIBLE BEARING LINERS Filed May 29, 1967 '3 Sheets-Sheet l /Z /9 Z5 Z3 Z7 June 23, 1970 N. E. FISHER ET AL 3,516,137

METHOD FOR MAKING THIN WALL FLEXIBLE BEARING LINERS 5 Sh0ts-Sheet 2 Filed May 29, 1967 wm k June 23, 1970 N. E. FISHER ET AL 3,516,137

METHQD'FOR MAKING THIN WALL FLEXIBLE BEARING LINERS Filed May 29, 1967 3 Sheets'Sheet :5

Patented June 23, 1970 3,516,137 METHOD FOR MAKING THIN WALL FLEXIBLE BEARING LINERS Norman Ernest Fisher, Harrow, John Whiteside, Naphill, and David Frederick Green, London, England, assignors to Vandervell Products Limited, London, England, a British company Filed May 29, 1967, Ser. No. 641,945 Claims priority, application Great Britain, June 3, 1966, 24,949/66; Jan. 20, 1967, 3,207/67 Int. Cl. B21d 53/10 US. Cl. 29-149.5 13 Claims ABSTRACT OF THE DISCLOSURE The invention provides a method of making thin walled flexible bearing liners in which a strip of material is fed step-by-step past a station at which portions of the strip are rendered arcuate whilst the strip is stationary and at a station at which arcuate portions are severed from the strip whilst the strip is stationary. The operations of rendering the strip arcuate and severing an arcuate portion from the strip are carried out at different times whilst the strip is stationary between movements so that longitudinal spreading of the strip caused by rendering a portion arcuate is not impeded by the severing operation.

This invention relates to a method of making thin wall flexible bearing liners, i.e. parts of split bearings, from metal strip, and which method is of the kind in which the strip at each of a number of positions along its length is subjected to a succession of different operations including severing portions from the strip across its width to provide the required axial length of the bearing liners and bending the metal into arcuate formation. It has previously been proposed first to bend a strip across its width, then successively to sever curved portions from it which were subsequently subjected to a number of operations to bring them to their finished form.

According to this invention a method of making thin wall flexible bearing liners comprises subjecting a strip of bearing material, at each of a number of locations along the length thereof, to a succession of different operations including rendering the strip arcuate across its width to bring it to the required degree of finish and successively severing from the arcuate strip arcuate portions of the required dimensions for the liners and upon which certain or all of the other operations have already been carried out.

The strip, before it is rendered arcuate may be subjected to an operation in which it is severed partly across its width from opposite edges thereof, the completion of which severing is effected after the operation which renders the strip arcuate across its width.

Preferably the rendering of the strip arcuate is carried out in a number of stages after it has been partially severed so that the unsevered portion is first rendered arcuate followed by the partially severed portions being rendered arcuate.

The strip may be rendered arcuate by a pressing operation.

The strip which has previously been rendered arcuate may be subjected to a further pressing operation which both presses the external surface of the arcuate portion and presses the parting faces at the ends of the arcuate portion and brings the external surface to its finished condition and required dimensions.

The rendering of one part of the strip arcuate by pressure and bringing the external surface of a previously formed arcuate portion to said finished condition and required dimensions are preferably carried out in the same press tool which also subjects the finished external arcuate surface of another portion to pressure so that whilst an arcuate portion of the strip is being subjected to pressure to bring its external surface to the finished condition and required dimension other portions of the strip on either side of it are also being subjected to pressure whereby axial spread of the intermediate portion is controlled.

In any of the methods referred to above the strip may be moved step by step past tools spaced apart along the length thereof by differences proportional to the step by step movement.

Also in any of the methods the strip before it is rendered arcuate may be subjected to an operation which reduces its width to a dimension which corresponds approximately to the circumferential length of the arcuate portions to allow for reduction to the final dimension by a subsequent operation.

In one particular method according to the invention the strip is traversed past tools spaced apart along its length and which tools carry out the aforesaid different operations and in which repeated operations on the strip along the length thereof reduce its width to form shoulders which are engageable with stationary stops and which strip during its reduction in width is held stationary by the tool which carries out that operation but is released by the tool when it has completed its operation whereupon the strip advances bringing resulting shoulders against the stops whereby the strip moves step by step, the aforesaid tools being spaced apart by distances proportional to the step by step movement of the strip.

In any of the methods referred to above those operations which tend to spread the strip along its length are carried out when the tools which carry out the other operations are free of the strip thus permitting the spread to take place.

Again in any of the methods referred to above the final severance of the arcuate portions from the strip may be followed by the formation of locating projections on the severed arcuate portions, which operations are successively carried out in one piece of apparatus.

Again in any of the methods referred to above the operation which completes the arcuate formation of the strip may bring the outer circumferential surface to a finished condition.

The inner circumferential surface of each severed arcuate portion may be brought to a finished condition by a machining operation.

In one specific method according to the invention the operations on the strip prior to the final severing of the arcuate portions comprise stamping identifying marks, indenting the fiat strip along lines across its width and opposite faces thereof to form chamfers, partially severing the strip across its width from opposite edges thereto and simultaneously bending the unsevered portion of the strip, completing the bending of the strip into arcuate formation in one or more stages, bringing the circumferential distance between the parting faces at the ends of the arcuate formation to an accurate and predetermined dimension and bringing the outer surface of the liner to the finished dimension and contour, rounding the inner edges of the parting faces, piercing oil holes with or without depressions around them and finally severing the arcuate portions and forming locating projections upon them.

The invention includes within its scope a thin wall arcuate flexible bearing liner formed with a number of layers and having a machined inner circumferential face and having at least a pressed outer circumferential face and pressed parting faces at the ends thereof.

The invention may also include within its scope a thin wall arcuate flexible bearing having pressed chamfer surfaces around the internal and external edges of each of its annular faces and having a recess with a pressed face on its internal circumferential surface with or without an oil hole in said recess, and having the pressed parting faces each having a pressed rounded edge between it and the internal circumferential face of the bearing.

The bearing liner may include all the features referred to in the last two paragraphs set out above.

The following is a more detailed description of the apparatus for carrying out a method such as is described above, reference being made to the accompanying drawings in which:

FIG. 1 is a diagrammatic side elevation of the two platens of a press between Which are located a number of press tools, units or capsules for carrying out the succession of operations;

FIG. 2 is a plan view of a continuous strip which is passed between the parts of the various press tools and showing one of the formed bearing liners after it has been severed therefrom;

FIG. 3 is a section on the line 33 of FIG. 1 in the direction of the arrows and showing the unit which effects the perforations of the oil holes;

FIG. 4 is an end elevation looking in the direction of the arrows 4-4 of FIG. 1;

FIG. 5 is a plan view of the lower part of a capsule showing the parts used for reducing the width of the strip, partially severing it and partially bending it;

FIG. 6 is a section on the line 66 of FIG. 1 showing the male portion of the die;

FIG. 7 is a section through part of the capsule which severs the finished bearing liner from the strip, in a plane parallel to a vertical plane containing the centre line of the strip and showing parts of the means for positioning the finished bearing liner for a further operation; and

FIG. 8 is a perspective view of a half bearing liner constructed according to the invention.

The invention is particularly applicable to the manufacture of interchangeable thin wall bearing liners from metal strips having a steel backing supporting bearing metal, for example comprising an intermediate layer of leadbronze, a1uminumtin or other alloy and a final thin bearing layer of a tin based or lead based alloy one such strip being described in Pat. No. 989,946 although a bi-metallic strip may be employed. The bearing layer may be non-metallic for example PTFE and lead or even a single layer or strip of suitable bearing material may be used.

As indicated above there may be provided between two platens 10 and 11 of a press a number of capsules for carrying out various operations on a strip of metal 12 from which flexible thin wall bearing liners are formed. The strip with the steel backing uppermost is fed step by step from left to right as viewed in FIG. 1 between parts of the capsules by, for example, driven nip rollers 8 mounted on a support 7 and having drive means indicated at 5. After leaving the nip rollers the strip passes through guide means 6 which locate the strip correctly with respect to tools in the capsules.

The strip when in the flat condition is passed through a first capsule where a number of operations specified later are carried out on it.

The capsule comprises upper and lower parts 13 and 14 which are constrained to move towards and away from each other by guide means (not shown) similar to that employed in another capsule shown in FIG. 4 so that the capsule can be removed from the press which upper and lower parts are engaged by the platens 10 and 11 respectively.

The first operation to be carried out on this capsule is the indentation of the upper surface of the strip as indicated at 9 in FIG. 2 by a tool 16 secured in a holder 17 attached to the upper part 13 of the capsule, during which operation the strip is supported by an upwardly directed face of a holder 18 secured by means (not shown) on the lower part 14 of the capsule. After one or more steps of the step by step movement of the strip it is brought above an indenting tool 19 in the holder 18, and by the downward movement imparted to the capsule part 13, the second operation of indenting the bearing metal on the underside of the strip is carried out. During this second operation the strip is located by the downwardly directed face of the holder 17.

The next step of the step by step movement brings the strip beneath a stamping tool 20 secured to the holder 17 attached to the upper part 13 of the capsule, and by the downward movement of the capsule part 13 the third operation of stamping a trademark and/or part number as indicated at 21 in FIG. 2 is carried out. During this operation the strip is supported by an upwardly directed face of the holder 18.

There may then follow one or more steps of the step by step movement in which no operation takes place.

The next step of movement of the stripbrings the aforementioned part of the strip between a pair of cutters 22 spaced at such a distance apart across the strip as to reduce its width to that corresponding to the circumferential length of the liner. The cutters (only one of which is shown in FIG. 1) are secured to the part 17. Each of the cutters 22 is formed as viewed in plan with two cutting edges at right angles and these cutting edges co-operate with the right angled cutting edges 23, 24 formed respectively on the parts 25 and 25a of shearing member 25a when the :part 10 of the press is caused to move downwardly and effect the fourth operation which results in marginal portions of a part of the strip being cut away to form shoulders 26 (FIG. 2). During the next step of movement of the strip, the shoulders 26 come into engagement with stops 27 (FIG. 5) fixed to the shearing member 25a. Whilst the shoulder is in engagement with the stop and the strip is stationary the platen 1-0 and the part 13 again move downwardly to cut away marginal portions of the preceding part of the strip thus reducing it in width and enabling the next step by step movement of the strip to be effected. This will bring the part of the strip which has been reduced in width between the female portion of a die 28 secured to the capsule part 13 and the male portion 29 of a die secured to the capsule part .14.

The centre portion 28a of the female die is formed part cylindrical and the outer portions of the die extend in an inclined manner from the cylindrical portion. Similarly the centre portion of the male die part 29 is part cylindrical as indicated at 30 in FIG. 5 and the portions extending laterally from the centre portion are inclined in a similar manner to that of the female die from the centre portion as indicated at 31.

The leading edges of the inclined outer portions of the female die are shearing edges and these are arranged to co-operate with the shearing faces 32 formed on the right hand end of the shearing member 25a. Thus during downward movement of the capsule part 13 fifth and sixth operations are carried out, the fifth due to the shearing edges of the female member forming cross cuts on each side of the strip extending only across a :part of the width of the strip whilst further downward movement of the capsule part 13 carries out the sixth operation in which the centre portion of the part of the strip is cylindrically bent and the other portions, which are separated by the cross cuts from the preceding part of the strip, will be brought into positions extending downwardly and outwardly from the centre portion by the inclined portions of the dies.

The next step of the step by step movement will bring the last part of the strip formed by the sixth operation between the left-hand portion 33 of a semi-cylindrical female die 34 as seen in FIG. -1 which is secured to the plate 13 and the left-hand male part of a die 35. The female portion of the die 34 has an axial length equivalent to the three step by step movements of the strip.

The male die part 35 is semi-cylindrical in shape and is supported by a pin 36 which extends through the smaller part of a stepped bore in an upper part 37 of the lower capsule part 14. The pin 36 has a flange 38 which is reciprocable in the larger part of the stepped bore and rests on the top of a number of spring discs 39 in the capsule part 14. When the capsule part 13 moves downwardly to effect a seventh operation the part of the strip under consideration is bent, by the outer ends of the male and female die parts 35 and 34, into semi-cylindrical form. The upper part 37 of the lower capsule part 14 is cut away at 37a so as to permit the ends of the arcuate liner to move downwardly from the upper face of the part 37 during which movement of the male part is descending and compressing the spring discs 39, and this operation is hereinafter referred to as first forming stage. As shown in FIG. 6 the upwardly directed face of the capsule part 37 along which the strip moves during the next two step by step movements is formed with grooves on opposite sides of the male die part 35 each of which grooves has vertical and inclined faces 40 and 41 joined by a curved portion 42. Thus in the first forming stage when the die part 34 ascends under the action of the press it will be followed by the male die part 35 under the action of the disc springs 39 and eventually the lower edges of the arcuate, now partly formed, liner will be brought above the level of the upper face of the part 37 and thus during the next step of the step by step movement these lower edges will be brought above the grooved portions of the part 37.

When the female die 34 is next moved downwardly by the capsule part 13 under the action of the press to effect the eighth operation in which the parting faces of the now formed liner are brought into engagement with the faces 40, 41 and 42, thus forming the bearing liner to the correct circumferential length between end parting faces and at the same time the curved faces 42 form curved corners at the inside of the parting faces. This eighth operation is referred to as the second forming stage and during this forming stage a preceding part of the strip is being subjected to coin pressing between the right-hand portions of the male and female die parts 34, 35 in a third forming stage thus controlling axial spread of the bearing liner in the direction of movement of the strip during the second forming stage.

The inclined faces 41 of the groove (FIG. 6) in the capsule part 37 applies appropriate corrective angles to the parting faces of a liner so that when it is sprung into a bearing housing the parting faces are diametrically fiat. The strip is prevented from curling upwards during the first and second forming stages by a superimposed arch shaped member 43 (FIG. 1) having a passage 44 therein communicating with a source of compressed air so as to blow away any loose particles which may collect between the die members 34, 35.

The strip then passes to another capsule indicated gen erally at 45 in FIG. 1 and an end view of which is shown in FIG. 3 where oil holes are punched in a ninth operation. It comprises a base portion 46 which is located in the platen 11 and from which base portion extend upwardly two arcuate portions 47 spaced apart across the width of the strip. Mounted between the two arcuate portions 47 are one or more angularly disposed blocks 48 (FIG. 3) according to the number of oil holes to be punched. Plungers 49 extend through holes in the blocks the axes of which plungers are disposed radial- 1y with respect to the curved portion 50 of the bearing liner. The plungers are provided with perforating punches which co-operate with die inserts 51a on a part 51 also mounted on the base 46. The inserts are shaped so as to form a depression around the inner side of each oil hole during the ninth operation or, if a punch is not provided, the shaped die alone may form a depression which holds a supply of lubricant. The upper ends of the plungers 49 are each engaged by one end 52 of a rocker which is pivot-ally mounted at 53 on a part 54 fixed to One of the blocks 48. The other end of each rocker is forked and rounded at 55 the limbs of which fork straddle a rod 56 fixed to the platen 10 and the rounded portion engages a washer 57 on the rod 56 which washer is supported by a nut 58 on the threaded lower extremity of the rod. It will be appreciated with this arrangement that as the platen 10 rises away from the platen 11 the ends 52 of the rockers are forced downwardly causing the arcuate portions 50 of the hearing liner to be perforated and this is at the time when those tools which tend to elongate the strip i.e. the tools 34 and 35 are inoperative thus allowing for the aforesaid longitudinal spread of the strip away from the abutment 27 to take place.

The strip finally passes between parts 59, 60 (FIG. 1) of a further unit or capsule where the finished bearing liner is severed from the strip in a tenth operation and a locating projection 62 is formed. The part 59 is constrained to move towards and away from the part 60 by guide rods 61 encircled by return springs 61a (see FIG. 4) and the part 60 is appropriately attached to the platen 11 by means not shown.

The part 59 has secured to it a die part 63 formed with a cutting edge 64 which co-operates with an inset shearing member 65 on a part 66 secured indirectly to the part 60 so as to complete the severing of the bearing liner as indicated at 67 in FIG. 2. The die part 63 is provided with a shoulder 68 around the bore to form a location for the loose liner.

It will be appreciated that it is most important that the locating projection 62 should be accurately positioned on the bearing liner since this determines the correct axial positioning of the liner in the bearing housing.

For this purpose the die part 63 is provided with the shoulder 68 (FIG. 1) which during the first part of the downward movement of the die part 59 is disposed forwardly of the bearing liner.

The part 66 carries two L shaped pusher pads 69' (FIG. 7) spaced apart at a distance slightly greater than the width of the shearing member 65 only one of which appears in FIG. 7. Each pusher pad has fixed to it a spindle 70 reciprocable in a hole in the part 66 which spindle is encircled by a set of disc springs 71 one end thereof engages the pusher pad and the other end engages a shoulder 72 at the end of a bore in the part 66.

The upper edges of the vertical limbs of each pad 69 are chamfered at 73, and the upper edges of the horizontal limbs are chamfered at 74. With this arrangement as the die part 63 moves downwardly carrying with it the liner the centre part of the latter is engaged by the shearing member 65 and at the same time the trailing edge of the liner on either side of the shearing members engages the chamfers 73 and the trailing edges of the parting faces engage the chamfers 74 on the pusher pads moving it against the action of the spring discs. As the centre part of the liner is finally severed the parts on either side of the centre will have reached the lower ends on the chamfers 73 and the trailing edges of the parting faces will have reached the lower ends of the chamfers 74. The liner will be shot forwardly by the pushers, and the leading edge of the arcuate liner is brought against the shoulder 68.

During the severing action the bearing is carried by a support 76 (FIG. 4) which in its turn is carried by a plate 77 mounted on springs 78 on the capsule part 60. Also mounted on the part 60 is a shearing and bending member 79 which engages an edge of the bearing part and, as the die part 63 continues to descend, forces the edge outwardly against a shearing edge or edges at a point 80 on the die 63 so as to shear through the edge of the bearing liner and force a tongue 62 outwardly to form a projection which subsequently locates the bearing part 67 in a hearing housing. This tongue or locating projection may be formed at an axial end of the parting faces of a bearing or at any position intermediate between the two ends. Since the combined effect of the severing operation and the operation forming the locating projection, tends to prevent longitudinal spreading of the strip it is preferably carried out at a different time to the coin pressing of the strip in the dies 34, 35 for which purpose the die part 63 may be mounted on a lever system in a similar manner to that described with reference to FIG. 3. After forming the eating projection the die part 63 moving upwardly causes the bearing liner to be forced downwardly by the underface of a part 81 fixed to the part 60 thus ejecting the loose bearing liner from the die part 63. The next step of the step by step movement pushes the bearing liner out of the apparatus.

The aforesaid capsules are so formed that stationary and movable guide parts are capable of having attached thereto different tools so as to enable different sized bearing parts to be formed by the same capsule.

It will be appreciated that although the above description and drawings show three capsules located in the same press, they might be located in separate presses and the strip might pass step by step from one press to another.

Also the tools for effecting the various operations referred to above might be distributed in the various capsules in a different manner to that described and shown. For example instead of the tools for indenting the strip along lines across the width of the strip and the tool for marking the strip being in the same capsule as the tools for partly severing the strip across its width and the tools for bending the strip they might be disposed in a separate capsule.

As previously indicated the internal surface of each severed bearing part may be brought to the finished state and required radial dimension in a separate apparatus as by machining e.g. broaching and in the case where an oil groove is required this may also be formed by a machining operation.

It will be appreciated that certain surfaces of a bearing liner may be formed by pressing operations and certain surfaces by machining operations in which case the pressing operations may be carried out in one or more capsules.

For example, the external semi-cylindrical surface of the bearing liner may be brought to the finished state by pressing operations in a single capsule following which operation the bearing liner may be transferred to a machine in which the internal surface is brought to the finished condition by a cutting operation. In certain cases the 10- cating projection may also be formed in a special purpose machine.

The initial thickness of the bearing metal from which the bearing liners are formed may vary from its outer edges to the centre where it is the thickest so that the operation described above which subjects the parting faces to pressure renders the thickness of the layer of bearing material in the finished bearing liner uniform.

A half bearing liner is illustrated in FIG. 8. In this case the liner has been formed from a tri-metallic strip having a steel backing 83 to which is bonded an intermediate layer of bearing metal 90 and a final thin bearing layer of a lead indium alloy 84. The liner has a pressed outer cylindrical surface 83 and a machined internal part cylindrical surface 84 in which there is formed a depression 85 having a pressed surface and at the bottom of which there is an oil hole 86. The inner edge of each parting surface 82 has a rounded pressed surface 87 and the annular surfaces at the sides of the liner have pressed chamfered faces 88, 89. A locating projection is indicated at 62 and is formed by the capsule shown in FIG. 4.

It will be appreciated that various modifications may be made to details of the construction without departing from the scope of the invention, for example, instead of the tool 20 for applying identifying marks to the strip and the tools 16 and 19 for indenting the upper and lower faces of the strip being in the same capsule 13 and 14 as the tools 22, 24, 28, 30, 34, 35 they could be in a separate capsule. Also where it is not required to press the parting faces in an oblique manner with rounded inner edges the capsule part 37 would not be provided with the recesses having the parts indicated at 40, 41 and 42. In certain instances it may not be necessary to provide the pusher pad 69 as shown in FIG. 7. Also instead of the parting faces being brought to their finished form by a pressing operation they might be machined in a separate apparatus.

Also in connection with the first capsule shown to the left of FIG. 1 it is preferable for the male die portion 35 to be divided into separate leading and trailing parts with respect to the direction of travel of the strip, the first and leading part being mounted on the spring supported plunger 36 and the second and trailing part being fixed to the capsule part 37, and is of such a height that its upper face is at a lower level than that of the first or leading part when that part is in its upper position and is level with the upper face of that part when it is in its lower position.

We claim:

1. A method of making thin walled flexible bearing liners in which a strip of bearing material is fed step by step past a number of stations at which different operations are carried out while the strip is stationary between movements which operations include rendering the strip arcuate across the width of the strip by pressing and subsequently severing arcuate portions from the strip, wherein the improvement comprises rendering a portion of the strip arcuate and severing an arcuate portion from the strip at different times whilst the strip is stationary between movements whereby axial spreading of the strip caused by the operation of rendering the strip arcuate is not impeded by the severing operation.

2. A method accoridng to claim 1 wherein at least one oil hole is punched in each arcuate portion of the Strip prior to the severing of the portions from the strip, the punching operation being carried out whilst the strip is stationary at a different time from the operation which renders the strip arcuate.

3. A method according to claim 1 wherein the strip, before it is rendered arcuate, is subject to an operation in which it is severed partly across its width from opposite edges thereof, the completion of which severing is effected after the operation which renders the strip arcuate across its width.

4. A method according to claim 2 wherein the operation for rendering the strip arcuate is carried out in a number of stages after it has been partially severed so that the unsevered portion is first rendered arcuate followed by the partially severed portions being rendered arcuate.

5. A method according to claim 1 wherein the operation which renders the strip arcuate is followed by an operation which brings the outer circumferential surface to a finished condition and required dimensions.

6. A method according to claim 5 wherein the part of the strip which has previously been rendered arcuate is subjected to a further pressing operation which both presses the external surface of the arcuate portion and presses the parting faces at the ends of the arcuate portion and brings said external surface to its finished condition and required dimensions.

7. A method according to claim 6 wherein simultaneously with the further pressing operation on a portion of the strip, the preceding adjacent portion is rendered arcuate by pressure and the succeeding adjacent finished portion is subjected to ressure, whereby axial spread of the first said portion is controlled during said further pressing operation upon it.

8. A method according to claim 1 wherein said strip is moved step by step past tools for effecting said operations spaced apart along the length thereof by distances equal to or equal to multiples of the axial length of the liners.

9. A method according to claim 1 wherein the strip before it is rendered arcuate is subjected to an operation which reduces its width to a dimension which corresponds approximately to the circumferential length of the arcuate portions, to allow for reduction to the final dimension by a subsequent operation.

10. A method according to claim 1 and in which the strip is traversed past tools spaced apart along its length and which tools carry out the aforesaid different operations and in which repeated operations on the strip along the length thereof reduce its width to form shoulders which are engageable with stationary stops and which strip during its reduction in width is held stationary by the tool which carries out that operation but is released by the tool when it has completed its operation whereupon the strip advances bringing resulting shoulders against the stops whereby the strip moves step by step, the tools being spaced apart by distances equal to or equal to multiples of the axial length.

11. A method according to claim 1 wherein the final severance of the arcuate portions from the strip is followed by the formation of locating projections on the severed arcuate portions, which operations are successively carried out in one piece of apparatus.

12. A method according to claim 1 wherein the inner circumferential surface of each severed arcuate portion is brought to a finished condition by a machining operation.

13. A method according to claim 1 wherein the operations on the strip prior to the final severing of the arcuate portions comprise stamping identifying marks, indenting the fiat strip along lines across its width and opposite faces thereof to form chamfers, partially severing the strip across its width from opposite edges thereof and simultaneously bending the unsevered portion of the strip, completing the bending of the strip into arcuate formation in one or more stages, bringing the circumferential distance between the parting faces at the ends of the arcuate formation to an accurate and predetermined dimension and bringing the outer surface of the liner to the finished dimension and contour, rounding the inner edges of the parting faces, punching oil holes with depressions around them and finally severing the arcuate portions and forming locating projections upon them.

References Cited UNITED STATES PATENTS 12/1930 Klocke.

9/1965 Hart et a1.

THOMAS H. EAGER, Primary Examiner 

